How can a multimeter be used to evaluate the quality of a circuit board?
In addition to measuring the measured object's resistance, the multimeter can also measure the DC voltage. Even the fundamental characteristics of transistors and the capacitance of capacitors can be measured by some multimeters. Understanding how to utilize multimeters to the best of your ability is one of the most fundamental abilities in electronic technology. Digital and pointer multimeters are both common types of multimeters.
The meter head is the main component of the pointer multimeter, which is a multifunctional measuring device. The pointer on the meter head reads the measured value. The liquid crystal display of the digital multimeter directly shows the measured value in digital form, making it easy to read. Some models additionally feature a voice prompt option. A multimeter is a type of meter with a head that houses an ohmmeter, an ammeter, and a voltmeter.
The multimeter's DC current file is a multiple-range DC voltmeter. By connecting the closed-circuit voltage dividing resistor in parallel with the meter head, the voltage range can be increased. The multimeter's DC voltage file is a multi-range DC voltmeter. The meter head's voltage range can be increased by connecting the voltage dividing resistor in series with it. The corresponding measuring ranges of various voltage dividing resistors vary.
1. Offline detection
Each IC chip pin's resistance to the ground, both positive and negative, should be measured. To identify the problem, compare it with a reliable IC chip.
2. Online detection
DC resistance is detected using the same technique as offline detection. But take note: The internal voltage of the multimeter should not be higher than 6V in order to disconnect the power supply on the circuit board that will be tested. Consider the impact of the periphery when measuring.
3. AC working voltage test method
To get the approximate value of the AC voltage on the IC, use a multimeter with a dB file. A 0.1-0.5F isolation DC capacitor can be placed in series with the positive test lead if there isn't a dB file. This approach is appropriate for ICs that operate at relatively low frequencies. The measured data are approximations because these signals will be influenced by the natural frequency and waveform, so it should be noted.
4. Total current measurement method
By measuring the total current of the IC power supply, the quality of the IC can be judged. Since most of the ICs are DC-coupled, when the IC is damaged (such as PN junction breakdown or open circuit), it will cause the subsequent stage to be saturated and cut off, and the total current will change. Therefore, measuring the total current can judge whether the IC is good or bad. The voltage on the loop resistance is measured online, and the current value can be calculated.
